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INDUSTRIAL ECOLOGY
Industrial Ecology is a field of study focused on the stages of the production processes of goods and services from a point of view of nature, trying to mimic a natural system by conserving and reusing resources
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SOLAR
GEOENGINEERING
Solar Geoengineering describes the range of engineering practices that seek to modify how much radiation the Earth receives from the sun. The most practical and popular is a method sometimes called SAI (Stratospheric Aerosol Injection) and is what's discussed here.
Solar Geoengineering is a controversial but emerging potential climate intervention whereby aerosol particles might be sprayed high in the sky to reflect out a small proportion of the incoming sunlight. The safest way to avoid climate change impacts would be to quickly slash greenhouse gas emissions all the way to zero, but humanity is proving reluctant to make that choice. Solar geoengineering is a technology that might partially compensate for our failure to cut greenhouse gas emissions, cooling the planet in a different manner. It would not eliminate the need for other climate solutions – most principally emissions reductions – but it could prove essential to maintaining relative climate stability in the next century.
Wake Smith is a Lecturer at the Yale School of the Environment, where he teaches a graduate level course on climate interventions. He is among the world’s leading authorities on the aeronautical practicalities and potential costs of solar geoengineering deployment.
THE THEORY
What's the problem?
The Earth has an energy budget, balancing incoming and outgoing flows of radiation to maintain a stable climate. Our ongoing emission of greenhouse gases has disturbed that balance, thickening the atmospheric blanket swaddling the Earth and trapping more heat in the climate system.
How does Solar Geoengineering help?
Solar geoengineering would compensate for that heat buildup by reflecting away a small fraction of the incoming sunlight. Less energy flowing out, but also less entering, thereby restoring energy balance at a lower temperature.
Watch to learn more about Earth's energy budget and how greenhouses gasses are changing the balance!​
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What can't Solar Geoengineering do?
It is widely agreed that solar geoengineering is not a perfect substitute for emissions reductions and should not be used as an excuse to continue greenhouse gas emissions. It is planetary morphine rather than penicillin, ameliorating symptoms without curing the underlying disease. Humanity still needs to chart a rapid course to net zero emissions and to thereafter undertake massive carbon removal and sequestration to fix the broken climate. However, transitioning away from fossil fuels and then draining down the atmospheric concentration of greenhouse gases they caused may take a century or more rather than a few decades. If that proves to be so, humanity may need relief from the enormous accumulation of heat that would ensue. Solar geoengineering would not be a magic “undo” button for climate change, but it could drastically reduce heating, and in a world that might otherwise be on a +3°C path, cooler temperatures could preserve societies and ecosystems that might otherwise wither.
It's happened before....
Not only does this sound sensible in theory, but it is regularly demonstrated in practice. The largest of volcanic eruptions such as Mount Pinatubo in 1991 have been documented to cool the planet substantially in the following year. However, the aerosols sediment out of the atmosphere after a year, so an aerosol layer designed to intentionally cool the planet would need to replenished continuously over a span of decades if not centuries.
While volcanoes spout off at random spots on the globe, cooling some geographies while little affecting others, a solar geoengineering program could be designed to cool the entire planet by injecting aerosols at certain latitudes in the tropics on both sides of the equator.
Mount Pinatubo eruption, 1991
HOW WOULD WE DO IT?
The Earth's atmosphere has five layers. To be effective, solar geoengineering aerosols must be placed in the lower stratosphere.
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If instead they are vented in the troposphere (the lowest layer of the atmosphere), they will return to the surface in days.
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Illustration of the most studied and likely most feasible Solar Geoengineering approach, Stratospheric Aerosol Injection. Adapted from SOURCE
If deployed higher up in the stratosphere, they will remain aloft for roughly a year. They will also be carried from the equator to the poles by a continuous atmospheric current (the Brewer-Dobson Circulation).
Consequently, a steady stream of injection both north and south of the equator would envelop the entire planet in a protective veil.
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The high altitude requirement means that solar geoengineering could not be done with existing aircraft, instead requiring a new fleet of hundreds of specially designed high-flying tankers. It might take two decades to put in place the lofting infrastructure, so this should not be conceived as an “emergency” solution.
Pathways to Explore
Research
While scientific theory, volcanic eruptions, and computer modelling all suggest that solar geoengineering could be very effective, no field tests in the stratosphere have been undertaken. Consequently, the risk of unanticipated impediments or consequences is quite real and can only be reduced by a rigorous research and field testing program, which has yet to commence.
Governance
An even greater shortfall lies in the governance arena. It is unclear who should be in charge of setting the global thermostat and how decisions could be made in a just and representative fashion. Solar geoengineering could be the source of geopolitical tensions, and since nearly all deployment scenarios would have transboundary if not global implications, responsible deployment may require a degree of international cooperation that may be beyond humanity’s grasp. For these reasons and others, it should be approached with deliberation and caution.
Here are some further resources about Solar Geoengineering:
Footnotes
NA as of now